While the press is full of coverage regarding GM's losses and cash needs, nobody ever seems to mention what their balance-sheet looks like. So I downloaded the 2007 annual report (2008 not available yet), and lo and behold, they had a negative equity of -40 bn US$ as of 12/31/07. That's before taking into account 30 bn US$ of losses in 2008, so their latest number should be around -70 bn US$. That's assuming they are a "going concern", which is a bit doubtful right now. Taking into account further costs for downsizing, restructuring etc., the "real" equity shortfall is probably 100 bn US$ or more.
Good luck to shareholders, bondholders and American taxpayers, if they seriously plan on recovering even small parts of their money!